On Mon 2017-12-18 11:40:59, Enric Balletbo Serra wrote: > Hi Pavel, > > 2017-12-15 21:57 GMT+01:00 Pavel Machek <pa...@ucw.cz>: > > Hi! > > > >> Yes, I think that how you describe luminance and lightness is right, > >> and sounds good improve the doc. > >> > >> To be clear the correction table for PWM values can be calculated with > >> this code. > >> > >> OUTPUT_SIZE = 65535 # Output integer size > >> INPUT_SIZE = 2047 > >> > >> def cie1931(L): > >> L = L*100.0 > >> if L <= 8: > >> return (L/902.3) > >> else: > >> return ((L+16.0)/116.0)**3 > >> > >> x = range(0,int(INPUT_SIZE+1)) > >> y = [int(round(cie1931(float(L)/INPUT_SIZE)*(OUTPUT_SIZE))) for L in x] > > > > Can we just generate the table on the fly? Should not be hard to do in > > fixed point, right? > > This was discussed a bit in previous RFC which had the code to > generate the table on the fly, see [1]. The use of a fixed table or an > on the fly table is something that I'll let the maintainers to decide. > I've no strong opinion on use the on the fly table if someone takes > care to review deeply the fixed point maths :)
You are free to pre-compute the table at boot. And you can even
compare the built-in and pre-computed table at boot, to make sure you
made no mistakes :-).
Pavel
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